<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app">
    x: {{ x }} <br>
    y: {{ y }} <br>
  </div>
  <script type="module">
    import { createApp, reactive, onMounted, onUnmounted, toRefs } from './node_modules/vue/dist/vue.esm-browser.js'

    function useMousePosition () {
        const position = reactive({
          x: 0,
          y: 0
        })

        const update = e => {
          position.x = e.pageX
          position.y = e.pageY
        }

        onMounted(() => {
          window.addEventListener('mousemove', update)
        })

        onUnmounted(() => {
          window.removeEventListener('mousemove', update)
        })

        return toRefs(position)
    }

    const app = createApp({
      setup () {
        // const position = useMousePosition()
        const {x, y} = useMousePosition()
        return {
          x, y
        }
      }
    })
    console.log(app)

    app.mount('#app')
  </script>
</body>
</html>